interface Doctrine_Query_Listener {
    preDqlDelete(..)
    preDqlUpdate(..)
}

class MyUserSoftDeleteQueryListener implements Doctrine_Query_Listener {
    public function preDqlDelete($query) {
        // put the code here that parses the from dql parts to see if the "User" class is involved
        // this code can be considered for addition in Doctrine_Query if implemented properly (($query->containsClass('User') ?)
        // then modify the query here as needed
    }
}

Doctrine_Connection {
  ...
  protected $_queryListeners;

  public function addQueryListener(Doctrine_Query_Listener $listener) {
  ...
  }

  public function removeQueryListener(Doctrine_Query_Listener $listener) {
  ...
  }
}

Doctrine_Query {
   ...
   protected function _preQuery() {
      foreach ($this->_conn->getQueryListeners() as $listener) {
          when dql delete:
              $listener->preDqlDelete()
          when update
              $listener->preDqlUpdate()
          ...
      }
   }
}


// in bootstrap code
$conn->addQueryListener(new MyUserSoftDeleteQueryListener());


if you want to have the query modifications in your model, make the model the query listener, although i would consider that not as pretty since it puts 2 separate responsibilites into one class.

class MyUser extends Doctrine_Record implements Doctrine_Query_Listener {
// ... model stuff

  public function preDqlDelete($query..) {
   ....
  }

  public function preDqlDelete($query..) {
   ....
  }

}

// bootstrap
$conn->addQueryListener(new MyUser()); // MyUser is a Query listener after all, even if this may look strange to you